As high capacity hauling vehicles have high loaded weight requirements and function on very rugged terrain, they present suspension problems different from those encountered in more conventional vehicles. The vehicle payload may vary by hundreds of tons. As a result, the suspension must support a wide range of weight.
In order to permit economic component geometry for efficient vehicle packaging, the total suspension stroke must be relatively short. Due to such vehicle space restrictions, these high capacity vehicles commonly utilize so-called "uncompensated" hydropneumatic suspension systems. In an uncompensated system, the volumes of fluid and mass of gas in each suspension strut remain constant. Consequently, to prevent the unit from bottoming out with road inputs in a loaded vehicle, the suspension must become rapidly stiffer as the weight supported increases. As a result, conventional uncompensated suspension systems typically are characterized by poor ride quality and high frame stresses due to load and road inputs. Because a large number of heavy duty vehicles with uncompensated suspension systems are currently utilized in bulk moving operations such as strip mining, it is desirable to develop a method to modify these field vehicles to improve such characteristics. Likewise, such a system would be advantageous in new vehicles where the vehicle design restricts the dimensions of the suspension package.